The present invention relates to a fixture for manufacturing magnets. More specifically, the present invention relates to a fixture and method for pressing and orientating magnets for voice coil actuator motors.
Disk drives are widely used in computers and data processing systems for storing information in digital form. Disk drives typically utilize one or more rotating, storage disks and a plurality of data transducers to interact with each storage disk. An E-block having a plurality of spaced apart actuator arms retains the data transducers proximate each storage disk. An actuator motor moves the E-block and the data transducers relative to the storage disks.
The need to rapidly access information has led to disk drives having storage disks which are rotated at ever increasing speeds and an actuator motor which moves the E-block at ever increasing rates. Unfortunately, this typically results in increased heat, noise and power consumption of the disk drive.
FIG. 1A illustrates a rear perspective view of a portion of a prior art, rotary, voice coil actuator motor 10P. In this embodiment, a flat, trapezoidal shaped coil 12P is positioned between two permanent magnets 14P and two flux return plates 16P. The coil 12P is secured to the E-block (not shown in FIG. 1A). Current passing through the coil 12P causes the coil 12P to move relative to the permanent magnets 14P to move the E-block.
One factor which effects efficiency of the actuator motor 10P is the strength of the magnets 14P. In the prior art actuator motor 10P illustrated in FIG. 1A, the magnets 14P include magnetization lines 18P (illustrated as arrows) which are oriented substantially perpendicular to the coil 12P. In this embodiment, the magnets 14P are made of a magnetic powder which is also oriented substantially perpendicular to the coil 12P.
FIG. 1B illustrates a cross-sectional view of a prior art fixture 22P which can be used to manufacture the magnet 14P. The prior art fixture 22P includes a fixture body 24P, an upper punch 26P, and a lower punch 28P. This fixture body 24P defines a cavity for receiving magnet powder to form the magnet 14P. An orientating coil 30P creates a magnet field 32P having flux lines which orient the magnet powder in the magnet 14P.
Unfortunately, the strength of the magnets 14P illustrated in FIG. 1A vary approximately 14-20 percent across the stroke of the coil 12P. More specifically, the strength of the magnets 14P is high, near the center and drops near the sides of the magnets 14P. This non-linearity causes difficulty in precisely moving the coil 12P. Inaccurate positioning of the coil 12P leads to data transfer errors between the data transducers and the storage disks.
In light of the above, it is an object of the present invention to provide an improved magnet and a fixture for making the improved magnet. It is another object to provide a fixture for manufacturing a magnet which is relatively easy to use. Yet another object is to provide a method for manufacturing a magnet which significantly improves the strength and performance of the magnet.
A manufacturing fixture which satisfies these needs is provided herein. The manufacturing fixture is useful for manufacturing a magnet from a magnet powder for a motor. The manufacturing fixture includes a fixture body and an orientating device. The fixture body includes a fixture cavity for receiving the magnetic powder. The orientating device aligns the magnetic powder in the fixture cavity.
The fixture cavity includes a cavity axis, a first cavity segment, second cavity segment, and a cavity transition between the first cavity segment and the second cavity segment. Uniquely, the orientating device creates a magnetic field having flux lines which extend (1) substantially transverse to the cavity axis near the cavity transition, (2) highly angled relative to the cavity axis near a perimeter of the fixture cavity and, (3) substantially parallel to the cavity axis intermediate the perimeter and the cavity transition.
The flux lines orient the magnet powder into a unique powder pattern which includes first region powder lines in a first region of the magnet which are substantially parallel with a first region axis and second region powder lines in a second region of the magnet which are angled relative to the first region axis.
This powder pattern subsequenuy facilitates a unique magnetization pattern in the magnet. This magnetization pattern results in higher magnetic flux densities throughout the magnet, higher magnetic flux densities at the parts of the magnet which interact with a coil of the motor, and higher average magnetic flux densities in the magnet.
Additionally, the higher magnetic flux densities at the sides of the magnet body, i.e. a greater radius, results in higher torques on the coil of the motor. This enables the magnet to generate more force from a given amount of current in the coil and increases the efficiency of the motor. This also reduces the amount of power consumed by the motor, reduces the amount of heat and noise generated by the motor during operation and increases operational time of the motor for a given battery charge. Further, the size of the magnet can be reduced for a given force requirement. These considerations are particularly important for computer disk drives, which often operate in heat and noise sensitive environments, or on battery power.
The present invention is also a method for manufacturing a magnet. The method includes the steps of positioning a magnet powder in the fixture cavity of the manufacturing fixture and aligning a portion of the magnet powder in the fixture cavity with a magnetic field to form the powder pattern outlined above. The method can also include the step of magnetizing the magnet to include the magnetization pattern outlined above.
Importantly, the manufacturing fixture is used to make a magnet having a unique powder pattern. This powder pattern allows the magnet to accept a unique magnetization pattern which increases the amount of force generated for a given amount of current in the coil. This increases the efficiency, accuracy and performance of the actuator motor, thereby reducing data seek times and amount of power consumed by the actuator motor.